Referenced in: none

Automatically associated channels: Slo1

Title: Mechanisms of Rose Bengal inhibition on SecA ATPase and ion channel activities.

Authors: Ying-Hsin Hsieh, Ying-Ju Huang, Jin-Shan Jin, Liyan Yu, Hsiuchin Yang, Chun Jiang, Binghe Wang, Phang C Tai

Journal, date & volume: Biochem. Biophys. Res. Commun., 2014 Nov 14 , 454, 308-12

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/25450394

Abstract
SecA is an essential protein possessing ATPase activity in bacterial protein translocation for which Rose Bengal (RB) is the first reported sub-micromolar inhibitor in ATPase activity and protein translocation. Here, we examined the mechanisms of inhibition on various forms of SecA ATPase by conventional enzymatic assays, and by monitoring the SecA-dependent channel activity in the semi-physiological system in cells. We build on the previous observation that SecA with liposomes form active protein-conducting channels in the oocytes. Such ion channel activity is enhanced by purified Escherichia coli SecYEG-SecDF·YajC liposome complexes. Inhibition by RB could be monitored, providing correlation of in vitro activity and intact cell functionality. In this work, we found the intrinsic SecA ATPase is inhibited by RB competitively at low ATP concentration, and non-competitively at high ATP concentrations while the translocation ATPase with precursors and SecYEG is inhibited non-competitively by RB. The Inhibition by RB on SecA channel activity in the oocytes with exogenous ATP-Mg(2+), mimicking translocation ATPase activity, is also non-competitive. The non-competitive inhibition on channel activity has also been observed with SecA from other bacteria which otherwise would be difficult to examine without the cognate precursors and membranes.